Insulation and alignment of segmented stators for electric machines

ABSTRACT

A stator segment for a segmented stator of an electric machine includes insulative material configured for overlapping with insulative material of an adjacent stator segment to provide continuous insulation along a joint between the adjacent stator segments. Additionally, or alternatively, the stator segment can include one or more alignment tabs configured to engage a surface of an adjacent stator segment to inhibit relative axial movement between adjacent stator segments.

FIELD OF THE INVENTION

The present invention relates generally to electric machines havingsegmented stators, including stator segments having continuousinsulation and/or alignment features.

BACKGROUND OF THE INVENTION

A variety of segmented stator designs for electric machines are known.By definition, these segmented stators include multiple individualstator segments that are assembled together. Each stator segmenttypically includes a metal core formed of laminated steel and definingyoke and tooth portions. An insulative material is typically positionedon one or more portions of each metal core to prevent direct contract(or arcing) between the metal cores and magnet wire wound around thestator teeth.

In the assembled segmented stator, the insulative material of eachstator segment typically abuts the insulative materials of adjacentstator segments along their side edges. However, any gap between theseadjacent insulative materials presents a potential arc path—betweenmagnet wire on the stator teeth and the stator segments' metalcores—that can result in electrical shorting. For this reason,insulative paper is sometimes placed over the metal joints betweenadjacent stator segments. Alternatively, the amount of wire wound aroundthe stator teeth is sometimes limited to ensure adequate clearancebetween the magnet wire and the metal cores. Additionally, fixturingtools and devices are commonly employed when assembling segmentedstators to align the end faces of the individual stator segments withone another.

As recognized by the present inventors, existing designs for segmentedstators and stator segments are disadvantaged in several respects. Forexample, the use of insulative paper along the joints between adjacentstator segments increases the manufacturing complexity and cost ofsegmented stators. Similarly, the use of fixturing tools for aligningthe end faces of adjacent stator segments increases the manufacturingcomplexity and cost of segmented stators. Further, limiting the amountof magnet wire wound about the stator teeth can adversely affect theperformance or efficiency of the segmented stator.

SUMMARY OF THE INVENTION

The present inventors have succeeded at designing stator segments for asegmented stator having continuous insulation and/or alignment features.

According to one aspect of the invention, a stator segment for asegmented stator includes a yoke portion, a tooth portion, and aninsulative material. The insulative material extends along at least oneside edge of the yoke portion and is configured for overlapping withinsulative material of an adjacent stator segment when assembledtogether in the segmented stator to thereby provide continuousinsulation along a joint between the adjacent stator segments.

According to another aspect of the present invention, a stator segmentfor a segmented stator includes a yoke portion, a tooth portion, and atleast a first tab extending from the yoke portion and configured toengage a surface of an adjacent stator segment when assembled togetherin the segmented stator to thereby inhibit relative axial movementbetween the adjacent stator segments.

According to yet another aspect of the invention, a segmented stator foran electric machine includes a plurality of annularly arranged statorsegments. Each stator segment includes a yoke portion, a tooth portionand insulative material. The yoke portions define a wall from which thetooth portions extend. The insulative material of at least one statorsegment overlaps with the insulative material of an adjacent statorsegment along a portion of the wall to thereby provide continuousinsulation over said portion of the wall.

According to another aspect of the invention, a segmented stator for anelectric machine includes a plurality of annularly arranged statorsegments. Each stator segment includes a yoke portion, a tooth portion,and a pair of tabs extending from opposite side edges and opposite endfaces of the yoke portion. The pair of tabs of each stator segmentengage top and bottom surfaces of adjacent stator segments to inhibitrelative axial movement between the plurality of stator segments.

According to still another embodiment of the invention, a segmentedstator for an electric machine includes a plurality of annularlyarranged stator segments. Each stator segment includes a yoke portion, atooth portion, a metal core, insulative material positioned over themetal core, and a pair of tabs extending from opposite side edges of theyoke portion. The pair of tabs of each stator segment engage surfaces ofadjacent stator segments to inhibit relative axial movement between theplurality of stator segments. Further, the insulative material of eachstator segment define a tongue and a groove on opposite side edges ofthe stator segment's yoke portion. The tongue and the groove of eachstator segment engaging the groove and tongue, respectively, of adjacentstator segments to provide continuous insulation along joints betweenthe metal cores of adjacent stator segments.

Further aspects of the present invention will be in part apparent and inpart pointed out below. It should be understood that various aspects ofthe invention may be implemented individually or in combination with oneanother. It should also be understood that the detailed description anddrawings, while indicating certain exemplary embodiments of theinvention, are intended for purposes of illustration only and should notbe construed as limiting the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of a stator segment according to oneexemplary embodiment of the present invention.

FIG. 1B is a side view of the stator segment of FIG. 1A.

FIG. 2 is a perspective view of two stator segments according to FIG. 1assembled together.

FIG. 3 is a partial perspective view of a joint between the adjacentstator segments of FIG. 2.

FIG. 4 is a perspective view of a segmented stator assembly according toanother preferred embodiment of the present invention.

Like reference symbols indicate like elements or features throughout thedrawings.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Illustrative embodiments of the invention are described below. In theinterest of clarity, not all features of an actual implementation aredescribed in this specification. It will be appreciated that in thedevelopment of any actual embodiment, numerous implementation-specificdecisions must be made to achieve specific goals, such as performanceobjectives and compliance with system-related, business-related and/orenvironmental constraints. Moreover, it will be appreciated that suchdevelopment efforts may be complex and time-consuming, but wouldnevertheless be a routine undertaking for those of ordinary skill in theart having the benefit of this disclosure.

A stator segment for a segmented stator of an electric machine accordingto a first exemplary embodiment of the present invention is illustratedin FIGS. 1A and 1B (sometimes referred to collectively as “FIG. 1”) andindicated generally by reference numeral 100. As shown in FIG. 1, thestator segment 100 includes a yoke portion 102, a tooth portion 104, andelectrically insulative material 106. The insulative material 106 coversportions of the stator segment 100 and electrically insulates suchportions from, among other things, wire wound around the tooth portion104 when the stator segment 100 is incorporated into a wound segmentedstator assembly, as further explained below.

In the embodiment of FIG. 1, the insulative material 106 extends alongopposite side edges 108, 110 of the yoke portion, and is configured foroverlapping with the insulative material of adjacent stator segments. Inparticular, the insulative material 106 defines a tongue 112 on one sideedge 108 and a groove 114 on the other side edge 110. The tongue 112 isconfigured for engaging a groove in a like stator segment positionedadjacent the side edge 108. The groove 114 is configured for engaging atongue in a like stator segment positioned adjacent the side edge 110.As shown in FIG. 1B, the tongue 112 and the groove 114 extend along theentire length of the side edges 108, 110, respectively.

FIG. 2 illustrates two stator segments 100A, 100B that are connectedtogether and identical to the stator segment 100 of FIG. 1. As shown inFIG. 2, the tongue 112B of stator segment 100B is received within thegroove 114A of stator segment 100A. In this manner, the insulativematerial 106A of stator segment 100A overlaps the insulative material106B of stator segment 100B along a joint 202 between the adjacentstator segments 100A, 100B. Due to this overlapping insulation, there isno direct arc path (to the underlying metal cores) between theinsulative materials 106A, 106B along the joint 202. In this manner, acontinuous insulation barrier is provided along the joint 202 betweenthe adjacent stator segments 100A, 100B.

As further shown in FIG. 2, the insulative materials 106A, 106Bpreferably cover a wall 204 defined by the adjacent yoke portions 102A,102B, as well as the tooth portions 104A, 104B which extend from thewall 204. In this manner, and in combination with the overlappinginsulation provided along the joint 202, the insulative materials 106A,106B form a continuous insulation barrier between the typicallylaminated metal (e.g. steel) cores which define the yoke portions 102A,102B and the tooth portions 104A, 104B, and wire wound around the toothportions 104A, 104B when the stator segments 100A, 100B are incorporatedinto a wound segmented stator assembly.

As best shown in FIG. 3, the tongue 112B and the groove 114A each have atriangular shape, as viewed from an end face 124 of the stator segments.It should be understood, however, that various other shapes can beemployed for the tongue and the groove, and that various otheroverlapping insulation configurations can be employed to eliminatedirect arc paths, without departing from the scope of the presentinvention. FIG. 3 further illustrates how, in this particularembodiment, the insulative materials 106A, 106B overlap one anotheralong a joint 208 between the metal cores 119A, 119B of the adjacentstator segments 100A, 100B.

Referring again to FIG. 1, because the stator segment 100 is providedwith the tongue 112 along one side edge 108 and the groove 114 along theopposite side edge 110, the stator segment 100 has a modularconstruction. In other words, the stator segment 100 can be annularlyarranged and joined with additional identical stator segments 100 toform a segmented stator. Alternatively, the stator segment 100 could beprovided with, for example, a tongue on both side edges 108, 110 formating with adjacent stator segments having complementary grooves. Insuch a case, however, at least two distinct stator segmentconfigurations must be employed to form a segmented stator assembly. Thestator segment 100 could also be provided with multiple tongues and/ormultiple grooves, or otherwise provided with insulative materialconfigured to overlap the insulative material of an adjacent statorsegment, without departing from the scope of the present invention.

In the embodiment of FIG. 1, the insulative material 106 is formed onthe yoke and tooth portions 102, 104 via overmolding. In other words,the insulative material 106 (e.g., Thermoplastic/Thermoset) is moldedover portions of the steel core 119A which defines the yoke and toothportions 102, 104. Among other advantages, overmolding can be used toensure each stator segment 100 has generally uniform dimensions, despiteany size variations in the underlying steel core. In the embodiment ofFIG. 1, the insulative material 106 has a minimum thickness of about0.094 inches. Alternatively, the insulative material 106 can be formedseparately (for example, as an insulative cap or end caps) using anysuitable material and material thickness, and then assembled onto thestator segment 100.

FIG. 4 illustrates a segmented stator assembly 400 according to anotherpreferred embodiment of the present invention. The stator assembly 400is constructed from multiple stator segments 100A-100L that are eachidentical to the stator segment 100 of FIG. 1. In the embodiment of FIG.4, twelve stator segments 110A-100L are employed to form a ten pole,twelve slot stator assembly 400. It should be understood, however, thatother numbers of stator segments, and other pole/slot combinations, canbe employed without departing from the scope of the invention.

Additionally, FIG. 4 illustrates winding material 402 (e.g., copperwire, aluminum wire, etc.) would around each tooth portion of the statorsegments. As should be apparent from the description above, the windingmaterial 402 is electrically isolated from the steel core of each statorsegment by the continuous insulation barrier (including the overlappinginsulative materials) formed on the wall 204.

With further reference to FIG. 1B, the stator segment 100 is alsoprovided with two alignment tabs 120, 122 extending from the yokeportion 102 and configured to engage surfaces of adjacent statorsegments. These tabs inhibit relative movement in the axial direction(i.e., a direction parallel to a center axis of the segmented stator andelectric machine) between adjacent stator segments, as further explainedbelow. In the embodiment of FIG. 1B, the tabs 120, 122 are provided onopposite side edges 108, 110 and opposite end faces 124, 126 of the yokeportion 102. It should be understood, however, that more or less tabscan be provided on the stator segment 100, and in different locationsthan tabs 120, 122, without departing from the scope of the presentinvention.

As shown in FIGS. 2 and 3, tab 120B of stator segment 100B engages a topend face 124 of the adjacent stator segment 100A. As a result, tab 120Bprevents relative movement between the adjacent stator segments 100A,100B in a first axial direction. Similarly, tab 122B of stator segment100B is configured to engage a bottom end face 126 of an adjacent statorsegment 100C (not shown in FIG. 2). As a result, tab 122B preventsrelative movement between the adjacent stator segments 100B, 100C is asecond axial direction, which is opposite the first axial direction.Thus, when multiple stator segments 100 are incorporated into thesegmented stator assembly 400 of FIG. 4, the tabs 120, 122 of themultiple stator segments will, collectively, inhibit relative axialmovement, in both directions, between each adjacent pair of statorsegments. As a result, there is no need to use a fixturing device foraligning the end faces 124, 126 of the stator segments 100 whenproducing the segmented stator assembly 400 from the stator segments100A-100L.

The tabs 120, 122 of each stator segment 100 are preferably dimensionedsuch that adjacent stator segments can be snapped together (i.e., via aninterference fit) to releasable secure each stator segment to adjacentstator segments. With this configuration, the metal core of each yokeportion 102 is sandwiched between two tabs on each of its side edges108, 110. Further, each tab 120, 122 preferably extends over a jointbetween adjacent stator segments. This is best shown in FIG. 3, wheretab 120B is shown extending over the joint 208 between the steel cores119A, 119B of the adjacent stator segments 100A, 100B. Alternatively,other configurations can be employed for the alignment tabs. Further,the alignment tabs can be configured to engage any desired surface of anadjacent stator segment so as to inhibit relative axial movement betweenadjacent stator segments.

In the embodiment of FIG. 1, the tabs 120, 122 are defined by theinsulative material 106 via overmolding. Thus, the tabs 120, 122 areformed integrally with the tongue 112 and the groove 114 and otherportions of the insulative material 106. Alternatively, the tabs, tongueand groove can each be formed separately, via independent overmoldingprocess(es) and/or by manufacturing one or more of these partsseparately and then assembling such part(s) by hand or machine onto thestator segment 100. Further, in the embodiment of FIG. 1, tab 120 isconfigured to engage insulative material on a top end face of anadjacent yoke portion, and tab 122 is configured to engage the steelcore on a bottom end face of another adjacent yoke portion.

Although the alignment tab and overlapping insulation features are bothincorporated into the stator segment 100 of FIG. 1, and the segmentedstator assembly 400 of FIG. 4, it should be understood that suchfeatures can be readily implemented independent of one another. Forexample, the stator segment 100 can be provided with the overlappinginsulation feature but without one or more alignment tabs, or viceversa.

Those skilled in the art will recognize that the teachings of thepresent invention can be applied to various electric machines (includingmotors and generators) employing segmented stators, including thoseemploying outer rotor designs. Preferred applications include, but arenot limited to, climate control systems (including blower motors for airhandlers) and fluid pumps.

Those skilled in the art will recognize that various changes can be madeto the exemplary embodiments and implementations described above withoutdeparting from the scope of the present invention. Accordingly, allmatter contained in the above description or shown in the accompanyingdrawings should be interpreted as illustrative and not in a limitingsense.

1. A segmented stator for an electric machine, the stator comprising aplurality of annularly arranged stator segments including a first statorsegment and a second stator segment, each stator segment including ayoke portion having opposite end faces, a tooth portion and insulativematerial, the yoke portions defining a wall from which the toothportions extend in a radial direction, the first and second statorsegments positioned adjacent and contacting one another and defining ajoint between the wall of the first stator segment and the wall of thesecond stator segment, the joint extending between the opposite endfaces of the adjacent stator segments, the insulative material of thefirst stator segment covering at least a portion of the wall of thefirst stator segment and extending in a circumferential direction beyondthe joint between the adjacent stator segments, the insulative materialof the second stator segment covering at least a portion of the wall ofthe second stator segment and overlapping in the radial direction theinsulative material of the first stator segment, the insulativematerials of the adjacent stator segments providing no direct arc pathbetween the yoke portions of the adjacent stator segments and wire woundaround the tooth portions of the adjacent stator segments.
 2. Thesegmented stator of claim 1 wherein the adjacent stator segments includemetal cores in contact with one another along said joint.
 3. Thesegmented stator of claim 2 wherein the insulative material of thesecond stator segment overlaps the insulative material of the firststator segment along the joint between the adjacent stator segments. 4.The segmented stator of claim 3 wherein the insulative materials of theadjacent stator segments define a tongue and a groove, the tongue beingreceived within the groove along said joint.
 5. The segmented stator ofclaim 4 wherein the tongue and the groove each have a triangular shape.6. The segmented stator of claim 1 wherein each stator segment includesa metal core with the insulative material molded over the metal core. 7.The segmented stator of claim 1 wherein the insulative material of eachstator segment defines a tongue and a groove.
 8. The segmented stator ofclaim 7 wherein the tongue and the groove of each stator segment arepositioned on opposite side edges of the yoke portion.
 9. The segmentedstator of claim 8 wherein the tongue and the groove of each statorsegment extend an entire length of said opposite side edges.
 10. Thesegmented stator of claim 1 wherein the insulative material of eachstator segment overlaps the insulative material of an adjacent statorsegment along a joint between each adjacent pair of stator segments. 11.The segmented stator of claim 1 wherein each stator segment includes atleast a first tab extending from its yoke portion and engaging a topsurface of an adjacent stator segment to inhibit relative axial movementbetween adjacent stator segments.
 12. The segmented stator of claim 11wherein each stator segment includes a second tab extending from itsyoke portion and engaging a bottom surface of an adjacent statorsegment.